Navigation

SQLite is a C library that provides a lightweight disk-based database that
doesn’t require a separate server process and allows accessing the database
using a nonstandard variant of the SQL query language. Some applications can use
SQLite for internal data storage. It’s also possible to prototype an
application using SQLite and then port the code to a larger database such as
PostgreSQL or Oracle.

The sqlite3 module was written by Gerhard Häring. It provides a SQL interface
compliant with the DB-API 2.0 specification described by PEP 249.

To use the module, you must first create a Connection object that
represents the database. Here the data will be stored in the
example.db file:

importsqlite3conn=sqlite3.connect('example.db')

You can also supply the special name :memory: to create a database in RAM.

c=conn.cursor()# Create tablec.execute('''CREATE TABLE stocks (date text, trans text, symbol text, qty real, price real)''')# Insert a row of datac.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")# Save (commit) the changesconn.commit()# We can also close the connection if we are done with it.# Just be sure any changes have been committed or they will be lost.conn.close()

The data you’ve saved is persistent and is available in subsequent sessions:

importsqlite3conn=sqlite3.connect('example.db')c=conn.cursor()

Usually your SQL operations will need to use values from Python variables. You
shouldn’t assemble your query using Python’s string operations because doing so
is insecure; it makes your program vulnerable to an SQL injection attack
(see https://xkcd.com/327/ for humorous example of what can go wrong).

Instead, use the DB-API’s parameter substitution. Put ? as a placeholder
wherever you want to use a value, and then provide a tuple of values as the
second argument to the cursor’s execute() method. (Other database
modules may use a different placeholder, such as %s or :1.) For
example:

# Never do this -- insecure!symbol='RHAT'c.execute("SELECT * FROM stocks WHERE symbol = '%s'"%symbol)# Do this insteadt=('RHAT',)c.execute('SELECT * FROM stocks WHERE symbol=?',t)print(c.fetchone())# Larger example that inserts many records at a timepurchases=[('2006-03-28','BUY','IBM',1000,45.00),('2006-04-05','BUY','MSFT',1000,72.00),('2006-04-06','SELL','IBM',500,53.00),]c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)',purchases)

To retrieve data after executing a SELECT statement, you can either treat the
cursor as an iterator, call the cursor’s fetchone() method to
retrieve a single matching row, or call fetchall() to get a list of the
matching rows.

This constant is meant to be used with the detect_types parameter of the
connect() function.

Setting it makes the sqlite3 module parse the declared type for each
column it returns. It will parse out the first word of the declared type,
i. e. for “integer primary key”, it will parse out “integer”, or for
“number(10)” it will parse out “number”. Then for that column, it will look
into the converters dictionary and use the converter function registered for
that type there.

This constant is meant to be used with the detect_types parameter of the
connect() function.

Setting this makes the SQLite interface parse the column name for each column it
returns. It will look for a string formed [mytype] in there, and then decide
that ‘mytype’ is the type of the column. It will try to find an entry of
‘mytype’ in the converters dictionary and then use the converter function found
there to return the value. The column name found in Cursor.description
is only the first word of the column name, i. e. if you use something like
'as"x[datetime]"' in your SQL, then we will parse out everything until the
first blank for the column name: the column name would simply be “x”.

Opens a connection to the SQLite database file database. By default returns a
Connection object, unless a custom factory is given.

database is a path-like object giving the pathname (absolute or
relative to the current working directory) of the database file to be opened.
You can use ":memory:" to open a database connection to a database that
resides in RAM instead of on disk.

When a database is accessed by multiple connections, and one of the processes
modifies the database, the SQLite database is locked until that transaction is
committed. The timeout parameter specifies how long the connection should wait
for the lock to go away until raising an exception. The default for the timeout
parameter is 5.0 (five seconds).

SQLite natively supports only the types TEXT, INTEGER, REAL, BLOB and NULL. If
you want to use other types you must add support for them yourself. The
detect_types parameter and the using custom converters registered with the
module-level register_converter() function allow you to easily do that.

detect_types defaults to 0 (i. e. off, no type detection), you can set it to
any combination of PARSE_DECLTYPES and PARSE_COLNAMES to turn
type detection on.

By default, check_same_thread is True and only the creating thread may
use the connection. If set False, the returned connection may be shared
across multiple threads. When using multiple threads with the same connection
writing operations should be serialized by the user to avoid data corruption.

By default, the sqlite3 module uses its Connection class for the
connect call. You can, however, subclass the Connection class and make
connect() use your class instead by providing your class for the factory
parameter.

The sqlite3 module internally uses a statement cache to avoid SQL parsing
overhead. If you want to explicitly set the number of statements that are cached
for the connection, you can set the cached_statements parameter. The currently
implemented default is to cache 100 statements.

If uri is true, database is interpreted as a URI. This allows you
to specify options. For example, to open a database in read-only mode
you can use:

db=sqlite3.connect('file:path/to/database?mode=ro',uri=True)

More information about this feature, including a list of recognized options, can
be found in the SQLite URI documentation.

Registers a callable to convert a bytestring from the database into a custom
Python type. The callable will be invoked for all database values that are of
the type typename. Confer the parameter detect_types of the connect()
function for how the type detection works. Note that typename and the name of
the type in your query are matched in case-insensitive manner.

Registers a callable to convert the custom Python type type into one of
SQLite’s supported types. The callable callable accepts as single parameter
the Python value, and must return a value of the following types: int,
float, str or bytes.

Returns True if the string sql contains one or more complete SQL
statements terminated by semicolons. It does not verify that the SQL is
syntactically correct, only that there are no unclosed string literals and the
statement is terminated by a semicolon.

This can be used to build a shell for SQLite, as in the following example:

# A minimal SQLite shell for experimentsimportsqlite3con=sqlite3.connect(":memory:")con.isolation_level=Nonecur=con.cursor()buffer=""print("Enter your SQL commands to execute in sqlite3.")print("Enter a blank line to exit.")whileTrue:line=input()ifline=="":breakbuffer+=lineifsqlite3.complete_statement(buffer):try:buffer=buffer.strip()cur.execute(buffer)ifbuffer.lstrip().upper().startswith("SELECT"):print(cur.fetchall())exceptsqlite3.Errorase:print("An error occurred:",e.args[0])buffer=""con.close()

By default you will not get any tracebacks in user-defined functions,
aggregates, converters, authorizer callbacks etc. If you want to debug them,
you can call this function with flag set to True. Afterwards, you will
get tracebacks from callbacks on sys.stderr. Use False to
disable the feature again.

This method commits the current transaction. If you don’t call this method,
anything you did since the last call to commit() is not visible from
other database connections. If you wonder why you don’t see the data you’ve
written to the database, please check you didn’t forget to call this method.

Creates a user-defined function that you can later use from within SQL
statements under the function name name. num_params is the number of
parameters the function accepts (if num_params is -1, the function may
take any number of arguments), and func is a Python callable that is
called as the SQL function. If deterministic is true, the created function
is marked as deterministic, which
allows SQLite to perform additional optimizations. This flag is supported by
SQLite 3.8.3 or higher, NotSupportedError will be raised if used
with older versions.

The function can return any of the types supported by SQLite: bytes, str, int,
float and None.

The aggregate class must implement a step method, which accepts the number
of parameters num_params (if num_params is -1, the function may take
any number of arguments), and a finalize method which will return the
final result of the aggregate.

The finalize method can return any of the types supported by SQLite:
bytes, str, int, float and None.

Creates a collation with the specified name and callable. The callable will
be passed two string arguments. It should return -1 if the first is ordered
lower than the second, 0 if they are ordered equal and 1 if the first is ordered
higher than the second. Note that this controls sorting (ORDER BY in SQL) so
your comparisons don’t affect other SQL operations.

Note that the callable will get its parameters as Python bytestrings, which will
normally be encoded in UTF-8.

The following example shows a custom collation that sorts “the wrong way”:

This routine registers a callback. The callback is invoked for each attempt to
access a column of a table in the database. The callback should return
SQLITE_OK if access is allowed, SQLITE_DENY if the entire SQL
statement should be aborted with an error and SQLITE_IGNORE if the
column should be treated as a NULL value. These constants are available in the
sqlite3 module.

The first argument to the callback signifies what kind of operation is to be
authorized. The second and third argument will be arguments or None
depending on the first argument. The 4th argument is the name of the database
(“main”, “temp”, etc.) if applicable. The 5th argument is the name of the
inner-most trigger or view that is responsible for the access attempt or
None if this access attempt is directly from input SQL code.

Please consult the SQLite documentation about the possible values for the first
argument and the meaning of the second and third argument depending on the first
one. All necessary constants are available in the sqlite3 module.

This routine registers a callback. The callback is invoked for every n
instructions of the SQLite virtual machine. This is useful if you want to
get called from SQLite during long-running operations, for example to update
a GUI.

If you want to clear any previously installed progress handler, call the
method with None for handler.

Returning a non-zero value from the handler function will terminate the
currently executing query and cause it to raise an OperationalError
exception.

Registers trace_callback to be called for each SQL statement that is
actually executed by the SQLite backend.

The only argument passed to the callback is the statement (as string) that
is being executed. The return value of the callback is ignored. Note that
the backend does not only run statements passed to the Cursor.execute()
methods. Other sources include the transaction management of the Python
module and the execution of triggers defined in the current database.

This routine allows/disallows the SQLite engine to load SQLite extensions
from shared libraries. SQLite extensions can define new functions,
aggregates or whole new virtual table implementations. One well-known
extension is the fulltext-search extension distributed with SQLite.

You can change this attribute to a callable that accepts the cursor and the
original row as a tuple and will return the real result row. This way, you can
implement more advanced ways of returning results, such as returning an object
that can also access columns by name.

If returning a tuple doesn’t suffice and you want name-based access to
columns, you should consider setting row_factory to the
highly-optimized sqlite3.Row type. Row provides both
index-based and case-insensitive name-based access to columns with almost no
memory overhead. It will probably be better than your own custom
dictionary-based approach or even a db_row based solution.

Using this attribute you can control what objects are returned for the TEXT
data type. By default, this attribute is set to str and the
sqlite3 module will return Unicode objects for TEXT. If you want to
return bytestrings instead, you can set it to bytes.

You can also set it to any other callable that accepts a single bytestring
parameter and returns the resulting object.

See the following example code for illustration:

importsqlite3con=sqlite3.connect(":memory:")cur=con.cursor()AUSTRIA="\xd6sterreich"# by default, rows are returned as Unicodecur.execute("select ?",(AUSTRIA,))row=cur.fetchone()assertrow[0]==AUSTRIA# but we can make sqlite3 always return bytestrings ...con.text_factory=bytescur.execute("select ?",(AUSTRIA,))row=cur.fetchone()asserttype(row[0])isbytes# the bytestrings will be encoded in UTF-8, unless you stored garbage in the# database ...assertrow[0]==AUSTRIA.encode("utf-8")# we can also implement a custom text_factory ...# here we implement one that appends "foo" to all stringscon.text_factory=lambdax:x.decode("utf-8")+"foo"cur.execute("select ?",("bar",))row=cur.fetchone()assertrow[0]=="barfoo"con.close()

Returns an iterator to dump the database in an SQL text format. Useful when
saving an in-memory database for later restoration. This function provides
the same capabilities as the .dump command in the sqlite3
shell.

This method makes a backup of a SQLite database even while it’s being accessed
by other clients, or concurrently by the same connection. The copy will be
written into the mandatory argument target, that must be another
Connection instance.

By default, or when pages is either 0 or a negative integer, the entire
database is copied in a single step; otherwise the method performs a loop
copying up to pages pages at a time.

If progress is specified, it must either be None or a callable object that
will be executed at each iteration with three integer arguments, respectively
the status of the last iteration, the remaining number of pages still to be
copied and the total number of pages.

The name argument specifies the database name that will be copied: it must be
a string containing either "main", the default, to indicate the main
database, "temp" to indicate the temporary database or the name specified
after the AS keyword in an ATTACHDATABASE statement for an attached
database.

The sleep argument specifies the number of seconds to sleep by between
successive attempts to backup remaining pages, can be specified either as an
integer or a floating point value.

importsqlite3con=sqlite3.connect(":memory:")cur=con.cursor()cur.execute("create table people (name_last, age)")who="Yeltsin"age=72# This is the qmark style:cur.execute("insert into people values (?, ?)",(who,age))# And this is the named style:cur.execute("select * from people where name_last=:who and age=:age",{"who":who,"age":age})print(cur.fetchone())con.close()

execute() will only execute a single SQL statement. If you try to execute
more than one statement with it, it will raise a Warning. Use
executescript() if you want to execute multiple SQL statements with one
call.

Executes an SQL command against all parameter sequences or mappings found in
the sequence seq_of_parameters. The sqlite3 module also allows
using an iterator yielding parameters instead of a sequence.

importsqlite3classIterChars:def__init__(self):self.count=ord('a')def__iter__(self):returnselfdef__next__(self):ifself.count>ord('z'):raiseStopIterationself.count+=1return(chr(self.count-1),)# this is a 1-tuplecon=sqlite3.connect(":memory:")cur=con.cursor()cur.execute("create table characters(c)")theIter=IterChars()cur.executemany("insert into characters(c) values (?)",theIter)cur.execute("select c from characters")print(cur.fetchall())con.close()

Fetches the next set of rows of a query result, returning a list. An empty
list is returned when no more rows are available.

The number of rows to fetch per call is specified by the size parameter.
If it is not given, the cursor’s arraysize determines the number of rows
to be fetched. The method should try to fetch as many rows as indicated by
the size parameter. If this is not possible due to the specified number of
rows not being available, fewer rows may be returned.

Note there are performance considerations involved with the size parameter.
For optimal performance, it is usually best to use the arraysize attribute.
If the size parameter is used, then it is best for it to retain the same
value from one fetchmany() call to the next.

Fetches all (remaining) rows of a query result, returning a list. Note that
the cursor’s arraysize attribute can affect the performance of this operation.
An empty list is returned when no rows are available.

As required by the Python DB API Spec, the rowcount attribute “is -1 in
case no executeXX() has been performed on the cursor or the rowcount of the
last operation is not determinable by the interface”. This includes SELECT
statements because we cannot determine the number of rows a query produced
until all rows were fetched.

With SQLite versions before 3.6.5, rowcount is set to 0 if
you make a DELETEFROMtable without any condition.

This read-only attribute provides the rowid of the last modified row. It is
only set if you issued an INSERT or a REPLACE statement using the
execute() method. For operations other than INSERT or
REPLACE or when executemany() is called, lastrowid is
set to None.

If the INSERT or REPLACE statement failed to insert the previous
successful rowid is returned.

Exception raised for errors that are related to the database’s operation
and not necessarily under the control of the programmer, e.g. an unexpected
disconnect occurs, the data source name is not found, a transaction could
not be processed, etc. It is a subclass of DatabaseError.

Exception raised in case a method or database API was used which is not
supported by the database, e.g. calling the rollback()
method on a connection that does not support transaction or has
transactions turned off. It is a subclass of DatabaseError.

The type system of the sqlite3 module is extensible in two ways: you can
store additional Python types in a SQLite database via object adaptation, and
you can let the sqlite3 module convert SQLite types to different Python
types via converters.

As described before, SQLite supports only a limited set of types natively. To
use other Python types with SQLite, you must adapt them to one of the
sqlite3 module’s supported types for SQLite: one of NoneType, int, float,
str, bytes.

There are two ways to enable the sqlite3 module to adapt a custom Python
type to one of the supported ones.

This is a good approach if you write the class yourself. Let’s suppose you have
a class like this:

classPoint:def__init__(self,x,y):self.x,self.y=x,y

Now you want to store the point in a single SQLite column. First you’ll have to
choose one of the supported types first to be used for representing the point.
Let’s just use str and separate the coordinates using a semicolon. Then you need
to give your class a method __conform__(self,protocol) which must return
the converted value. The parameter protocol will be PrepareProtocol.

The underlying sqlite3 library operates in autocommit mode by default,
but the Python sqlite3 module by default does not.

autocommit mode means that statements that modify the database take effect
immediately. A BEGIN or SAVEPOINT statement disables autocommit
mode, and a COMMIT, a ROLLBACK, or a RELEASE that ends the
outermost transaction, turns autocommit mode back on.

You can control which kind of BEGIN statements sqlite3 implicitly
executes via the isolation_level parameter to the connect()
call, or via the isolation_level property of connections.
If you specify no isolation_level, a plain BEGIN is used, which is
equivalent to specifying DEFERRED. Other possible values are IMMEDIATE
and EXCLUSIVE.

You can disable the sqlite3 module’s implicit transaction management by
setting isolation_level to None. This will leave the underlying
sqlite3 library operating in autocommit mode. You can then completely
control the transaction state by explicitly issuing BEGIN, ROLLBACK,
SAVEPOINT, and RELEASE statements in your code.

Changed in version 3.6: sqlite3 used to implicitly commit an open transaction before DDL
statements. This is no longer the case.

Using the nonstandard execute(), executemany() and
executescript() methods of the Connection object, your code can
be written more concisely because you don’t have to create the (often
superfluous) Cursor objects explicitly. Instead, the Cursor
objects are created implicitly and these shortcut methods return the cursor
objects. This way, you can execute a SELECT statement and iterate over it
directly using only a single call on the Connection object.

importsqlite3persons=[("Hugo","Boss"),("Calvin","Klein")]con=sqlite3.connect(":memory:")# Create the tablecon.execute("create table person(firstname, lastname)")# Fill the tablecon.executemany("insert into person(firstname, lastname) values (?, ?)",persons)# Print the table contentsforrowincon.execute("select firstname, lastname from person"):print(row)print("I just deleted",con.execute("delete from person").rowcount,"rows")# close is not a shortcut method and it's not called automatically,# so the connection object should be closed manuallycon.close()

Connection objects can be used as context managers
that automatically commit or rollback transactions. In the event of an
exception, the transaction is rolled back; otherwise, the transaction is
committed:

importsqlite3con=sqlite3.connect(":memory:")con.execute("create table person (id integer primary key, firstname varchar unique)")# Successful, con.commit() is called automatically afterwardswithcon:con.execute("insert into person(firstname) values (?)",("Joe",))# con.rollback() is called after the with block finishes with an exception, the# exception is still raised and must be caughttry:withcon:con.execute("insert into person(firstname) values (?)",("Joe",))exceptsqlite3.IntegrityError:print("couldn't add Joe twice")# Connection object used as context manager only commits or rollbacks transactions,# so the connection object should be closed manuallycon.close()

Older SQLite versions had issues with sharing connections between threads.
That’s why the Python module disallows sharing connections and cursors between
threads. If you still try to do so, you will get an exception at runtime.

The only exception is calling the interrupt() method, which
only makes sense to call from a different thread.

The sqlite3 module is not built with loadable extension support by
default, because some platforms (notably Mac OS X) have SQLite
libraries which are compiled without this feature. To get loadable
extension support, you must pass –enable-loadable-sqlite-extensions to
configure.